What Is Hawthorn?

Gardeners in temperate climate regions often grow trees or shrubs that carry a colloquial name of hawthorn. These deciduous trees do have thorns on their branches, but their ornamental value in tiny, white flowers, bright fall leaf color and production of tiny red fruit that attracts birds. They grow in U.S. Department of Agriculture Plant Hardiness Zones 4 through 8, depending on species.

Hawthorns belong to botanical genus Crataegus, comprised of roughly 200 species native to the woodlands across various continents in the Northern Hemisphere. More common hawthorn species grown in garden settings include cockspur hawthorn (Crataegus crus-galli), yellow hawthorn (Crataegus flava), English hawthorn (Crataegus laevigata), tansy hawthorn (Crataegus tanacetifolia) and the Washington hawthorn (Crataegus phaenophorum).

While the precise mature size of hawthorn trees varies by species, they generally are small trees that range roughly from 20 to 30 feet in height. The trees develop singular but slender trunks that broaden in a rounded to spreading oval canopy of thorny branches. Some species form suckering shoots from their trunk and surface roots to form a shrubby thicket.

In spring to early summer as the leaves emerge and mature, hawthorn trees bear clusters of thousands of tiny, white, five-petaled flowers. Once pollinated by insects, each blossoms develops into a pea-sized fruit that looks like a tiny apple, ranging in color from orange to orange red or fiery scarlet, but a few species' fruit are yellow, black or blue green. The fruits persist on the branches even into early winter after leaves drop. The fruits attract birds and other wildlife and are plucked away by midwinter. Snow and ice accumulates on the thorny branches, creating an attractive silhouette.

Landscape architects and garden designers use hawthorns as small specimen trees or focal points. If planted in clustered groves or in rows, hawthorn trees become good hedges or screens since they produce many twigs and thorns. The "A-Z Encyclopedia of Garden Plants" mentions hawthorns tolerate many soil types that never become soggy and in landscapes exposed to ocean salt spray or constantly affected by wind.

Even though hawthorns are common in gardens, these trees carry some challenges in culture, particularly with susceptibility to pests and diseases. Local climate and the tree species determine exactly which insect pests or diseases manifest, but hawthorns typically battle tree borer, caterpillars, leafminer, leaf skeletonizer and scale insects. Diseases that affect apple trees also tend to wreak havoc on hawthorns, including fireblight, canker, cedar-apple rust, apple scab, powdery mildew and leaf fungal spot.

While hawthorn is most widely used as the common name for species in the plant genus Crataegus, gardeners in warm winter regions may refer to a shrub by the name hawthorn or more precisely as Indian hawthorn. It is an evergreen shrub bearing white to pale pink blossoms and black berries and belongs in the genus Rhaphiolepis. It grows in USDA Plant Hardiness Zones 7 through 11.